1. Field of the Invention
The present invention relates to an information processing apparatus, and more particularly to a technology for reducing power consumption in an information processing apparatus that has an oscillating circuit.
2. Description of the Related Art
A small sized portable electronic apparatus usually works on batteries. Therefore, in order to extend the life of the battery, one-chip microcomputers used in this kind of small sized portable electronic apparatus are desired to be able to operate in low voltage and to be of low power consumption.
In order to realize this, one-chip microcomputers are usually driven at an operating voltage of around 1 voltage and at an operating frequency of around 32 kHz.
However, when small sized portable electronic equipment is required to have an information processing capability to some extent, the operating frequency of 32 kHz is not enough for processing information.
In order to solve this problem, a twin-clock microcomputer that has an oscillating circuit with a low operating frequency of around 32 kHz and an oscillating circuit with a high operating frequency of around 4 MHz is proposed. In this twin-clock microcomputer, when high speed processing is required the microcomputer is driven at a high speed operating frequency, otherwise it is driven at a low speed operating frequency.
Operating frequency and power consumption is in a roughly proportional relationship, for that reason high speed processing is not desirable from the viewpoint of power consumption.
However, recently, there is a demand for high speed information processing in small sized portable electronic apparatus, and at the same time much less power consumption is desired.